Public AudioMixer assigned in Editor gives NullReference

- Originally posted this in Answers, but it's been awaiting moderation for three days now:


In the following code, I've assigned an Audio Mixer that I created to the masterMixer variable by dragging it in from the Project view to its public variable component in the Inspector:

However, whenever I try to use GetFloat/SetFloat as seen here, I'm given a NullReferenceException for masterMixer.

Now, the first thing I thought was that I needed to assign an actual instance of "Audio" in the scene to masterMixer, but there doesn't seem to be any way of actually placing an Audio Mixer in your scene.

I followed the official tutorial on exposing Audio Mixer parameters, but the only difference is that he's controlling SetFloat/GetFloat entirely through default UI stuff in the Inspector, whereas I'm triggering all changes through code. That shouldn't make a difference, right?

Code (CSharp):

1.     using UnityEngine;
2.     using System.Collections;
3.     using UnityEngine.Audio;
4.    
5.     public class AudioMixerControl : MonoBehaviour {
6.    
7.         public AudioMixer masterMixer;
8.        
9.         public float GetMusicVolume()
10.         {
11.             float vol;
12.             masterMixer.GetFloat("musicVolume", out vol);
13.             return vol;
14.         }
15.    
16.         public float GetSoundVolume()
17.         {
18.             float vol;
19.             masterMixer.GetFloat("soundVolume", out vol);
20.             return vol;
21.         }
22.    
23.    
24.         public void SetMusicVolume(float vol)
25.         {
26.             masterMixer.SetFloat("musicVolume", vol);
27.         }
28.    
29.         public void SetSoundVolume(float vol)
30.         {
31.             masterMixer.SetFloat("soundVolume", vol);
32.         }
33.     }
34.